The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Stirling engines refer to external combustion engines that convert thermal energy into kinetic energy by sealing a heating medium, such as hydrogen or helium, in an enclosed space, and compressing and expanding the heating medium at different temperatures.
Stirling engines have high thermal efficiency in theory of thermodynamics, and do not have an explosion stroke during combustion. Thus, these Stirling engines have lower vibration and noise, compared to conventional internal combustion engines. In addition, these Stirling engines have an advantage of utilizing all heat sources, such as wood fuel, factory waste heat, and solar heat, as well as petroleum, natural gas, and fossil fuel.
The principle of Stirling engines is known to be designed by Stirling, a British minister in 1816. However, the Stirling engines didn't come into the spotlight due to the rapid development of steam engines and internal combustion engines. In recent years, the Stirling engines have, however, received attention again since heat-resistant material and sealing techniques are newly developed and the importance of energy saving and alternative energy is emphasized.
As these Stirling engines, there are known an α-Stirling engine as illustrated in U.S. Pat. No. 7,171,811 (Feb. 6, 2007), a β-Stirling engine as described in U.S. Pat. No. 7,043,909 (May 16, 2006), etc. FIGS. 9 and 10 illustrate the shapes and driving methods of an α-Stirling engine and a β-Stirling engine, respectively. In the α-Stirling engine, a displacer is not provided therein, two respective pistons 1 and cylinders 2 are arranged to have a phase difference of 90°, and a heating medium 3 moves between a heat radiation cylinder and a heat absorption cylinder, as illustrated in FIG. 9. In the β-Stirling engine, a piston 1 and a displacer 4 are coaxially located, and the heating and cooling times of a heating medium 3 are adjusted by the displacer 4 so that a heat radiation function and a heat absorption function are performed according to the position of the piston in a single cylinder 2, as illustrated in FIG. 10.
However, we have discovered that the piston reciprocates in reciprocating type Striling engines such as the α-Stirling engine and the β-Stirling engine, vibration and noise are generated during the operation thereof. In addition, the heating medium may be leaked from the contact portion between the piston and the cylinder, and complicated driving mechanisms, such as pistons, cylinders, connecting rods, and cranks, are required. For this reason, manufacturing costs are increased and it is difficult to minimize engines.